Cop %r 6.3 /*. T /V ^VW^,i STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION DIVISION OF THE STATE GEOLOGICAL SURVEY FRANK W. DE WOLF. Chief Cooperative Mining Series BULLETIN 22 WATER-GAS MANUFACTURE WITH CENTRAL DISTRICT BITUMINOUS COALS AS GENERATOR FUEL \i\ BY W. W. ODELL, U. S. Bureau of Mines, and W. A. DtJNKLEY, State Geological Survey Division. ILLINOIS MINING INVESTIGATIONS Prepared under a cooperative agreement between the Illinois State Geological Survey Division, the Engineering Experiment Station of the University of Illinois, and the U. S. Bureau of Mines. PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS 1918 ILLINOIS MINING INVESTIGATIONS Cooperative Agreement GAS SECTION The difficulty, due to war conditions, of obtaining adequate and reliable delivery of eastern gas-coal and of coke has suggested the wider use in gas manufacture of low-sulphur coal mined in the central district, comprising Illinois, Indiana, and western Kentucky. The needs of the gas industry, and the desire of the U. S. Fuel Administration to meet those needs, has led to the appointment by Governor Frank O. Lowden, of a Technical Committee on Gas, By- products, and Public Utilities, to act in an advisory relation. The committee includes representatives of the Illinois Gas Association, the ,U. S. Bureau of Mines, the Engineering Experiment Station of the University of Illinois, and the State Geological Survey Division of the Department of Registration and Education, State of Illinois. Previously, some studies of the use of Illinois coal in retort-gas manufacture and in by-product coke ovens, and of the chemical and physical properties of Illinois coal, have been conducted under the Illi- nois Mining Investigations, cooperative agreement, — a joint agency of the U. S. Bureau of Mines, the University of Illinois, and the State Geological Survey Division. The continuation and expansion of this work has been recommended by the Technical Committee and the Fuel Administration. In response a Gas Section has been created, and experienced gas engineers, chemists, and other specialists have undertaken a program of experiment on a commercial scale to extend the use of central district coal in water-gas generators and in gas retorts. The results of the investigations will be published, and, in addi- tion, the operators of gas plants in the region naturally tributary to central district coal will be advised by the Technical Committee, of the progress from time to time, and will be urged to witness and par- ticipate in the tests and to introduce in their own plants new or im- proved practices which will lessen the burden on the railroads, and assist the mines and the coke ovens to meet the unprecedented demands due to the war. Inquiries and suggestions regarding the gas experiments should be addressed to Gas Section, Room 305 Ceramics Bldg., Urbana, Illi- nois. 3 3051 00006 4042 STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION DIVISION OF THE STATE GEOLOGICAL SURVEY FRANK W. DE WOLF, Cbief Cooperative Mining Series BULLETIN 22 WATER-GAS MANUFACTURE WITH CENTRAL DISTRICT BITUMINOUS COALS AS GENERATOR FUEL BY W. W. ODELL, U. S. Bureau of Mines, and W. A. DUNKLEY, State Geological Survey Division. ILLINOIS MININO INVESTIGATIONS Prepared under a cooperative agreement between the Illinois State Geological Survey Division, the Engineering Experiment Station of the University of Illinois, and the U. S. Bureau of Mines. PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS 1J)18 STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION DIVISION OF THE STATE GEOLOGICAL SURVEY Frank W. DeWolf, Chief Committee of the Board of Natural Resources and Conservation Francis W. Shepardson, Chairman Director of Registration and Education David Kinley Representing the President of the Uni- versity of Illinois Thomas C. Chamberlin Geologist CONTENTS PAGE Introduction 7 Objections offered to the use of bituminous coal as generator fuel. . . 10 Methods of overcoming objections 11 Water-gas manufacture at plants using bituminous coal fuel 13 Kind and size of fuel 14 Depth of fuel bed and its relation to blast and steam cycle 14 Quality and quantity of oil used 15 Distribution of oil in the carburetor 16 Purging the machine with air 16 Operating data from typical plants where coal is used as generator fuel 16 Discussion of table 19 The economical advantage of central district coal as a water-gas gen- erator fuel 20 Cost of materials 21 Cost of operating labor 22 Cost of repairs 22 Overhead and miscellaneous expense 22 Income from sale of residuals 23 Summary '. 23 Conclusions 24 Suggested problems for further study 24 Digitized by the Internet Archive in 2012 with funding from University of Illinois Urbana-Champaign http://archive.org/details/watergasmanufact22odel ILLUSTRATIONS FIGURE PAGE 1. Bituminous coal zone C 6 2. Bituminous coal zone D 8 3. Bituminous coal zone E 9 TABLES 1. Practice at four water-gas plants 18 2. A comparison of the approximate manufacturing costs of water-gas with coke and with coal as generator fuel 23 Fig. 1. — Bituminous coal zone C, established by the U. S. Fuel and the U. S. Rail- road Administrations, April 1, 1918, and corrected to October 1, 1918. Includes low-sulphur coal areas in southern Illinois. At the time this map was made, producing districts in Illinois were restricted in their shipments of coal during the winter to markets within and along the solid boundary line, and during the summer to markets within and along the heavy dashed boundary line and its solid continuation south from Albia, Iowa, and Milwaukee, Wisconsin. Under date September 26, 1918, this order was modified as follows: The Lower Peninsula of Michigan is to be included for the winter in Zone C. Those parts of Wisconsin and Minnesota lying between the solid and dashed lines in the figure may receive coal the entire year from Illinois. The period during which shipments may be made into South Dakota is extended to November 1. WATER-GAS MANUFACTURE WITH CENTRAL DISTRICT BITUMINOUS COALS AS GENERATOR FUEL By W. W. Odell, U. S. Bureau of Mines, and W. A. Dunkley, State Geological Survey Division INTRODUCTION This circular presents data on present water-gas manufacture, as gathered by the writers during an inspection of twenty water-gas plants in Illinois and surrounding states, in which bituminous coal from the central mining district of Illinois, Indiana, and western Kentucky is being used in place of coke as a generator fuel. The term "central district bituminous coals" as used in this paper refers to those origin- ating in this district. The generator fuel formerly used in these plants was either retort - house coke made usually from an eastern coal, or else oven coke trans- ported from a distance. Eastern coal produces a better coke in the gas retort than western coal, and therefore a coke that can be used to greater advantage in the water-gas set. This coke and the coke hauled direct from the east will give a greater production of gas from a water-gas set in a given time than will uncoked bituminous coal from either the east or the central district. I low ever, the well-known con- ditions prevailing at the present time in the coal and railroad industries make it desirable and perhaps necessary to haul as little coal or coke as possible from the eastern points of production to the central west. The use of central district bituminous coals as generator fuel will not During the entire year producing districts of Vermilion County, Illinois, along the Wahash Railway may in addition ship coal to points of delivery along the Wabash Railway within Indiana. Similarly, producing districts of Sangamon County may ship to stations along the Cincinnati, Indianapolis, and Western Railroad, as far east as Indianapolis, and including points of delivery within switching limits on connecting lines. Neither of these counties produces low-sulphur coal, however. A modification affecting the distribution of Jackson and Randolph county coals is as follows: All producers located along the Mobile and Ohio Railroad and short-line connec- tions in Illinois may ship coa! to points of delivery on the Mobile and Ohio Railroad within Tennessee and Mississippi, as far south as Meridian, Mississippi, including stations within switching limits on connecting railway lines. Jackson County is a producer of low-sulphur coal from seam No. 2. Consult the District Representative of the Fuel Administration, 2017 Fisher Building, Chicago, to learn decisions on suggested changes still pending. < >i these changes, the one affecting particularly the coal-gas industrj relates to the addition of a pari of Iowa to the territory of Zone C. WATER-GAS MANUFACTURE only reduce freight traffic but will release for other necessary uses coke now used as water-gas fuel. Furthermore, such successful prac- tice with these coals may be developed that a new permanent market for them will be established. For these reasons, it is desirable that central district coals be substituted for eastern coal and coke wherever possible. Fig. 2. — Bituminous coal zone D, established by the U. S. Fuel and the U. S. Rail- road Administrations, April 1, 1918, and corrected to October 1, 1918. Includes low-sulphur coal in western Indiana. As the zoning was originally established, all producing districts of Indiana were re- stricted in their shipments of coal to markets within and along the heavy boundary line. Under date September 26, this order was modified so as to include all of the Lower Penin- sula of Michigan in the territory of Zone D. Last winter the shortage of coke fuel at many water-gas plants led to some independent experimentation with bituminous coal of vari- ous sizes from districts in Illinois and Indiana where low-sulphur coal is mined. As a rule the results have been encouraging. The plants have been kept going, and under certain conditions central district coal as generator fuel has proven more economical than coke. This report outlines the difficulties which were anticipated, and those actually met and overcome in connection with the change of fuel ; and presents operating data from several plants at which central INTRODUCTION district coal is used successfully. Actual operating costs listed reveal no increase due to the use of bituminous coal ; in fact an actual saving is indicated where the capacity of the plant is ample. Houst Fig. 3. — Bituminous coal zone E, established by the U. S. Fuel and the U. S. Rail- road Administrations, April 1, 1918, and corrected to July 1, 1918. Includes low-sulphur coal in western Kentucky. Producing districts in western Kentucky, shown in hlack, are restricted in their ship- ments of coal to markets within or along the heavy houndary line. Modifications of the original zoning made prior to July 1, 1918, have been incorporated in the map. Later modifications affecting the gas-coal markets are as follows: Producers in the western Kentucky districts may in addition distribute their coal (1) along the Louisville, Cincinnati and Lexington Division of the Louisville and Nashville Railway between Louisville and Newport, Kentucky, inclusive, and (2) in Cincinnati, Ohio, and points of delivery located within the Cincinnati switching district. Producers of this district may not ship coal without permit into those parts of Illi- nois, Wisconsin, and Indiana, included originally in zone E as shown by the heavy boundary line. A provision is made, however, which should he noted by the coal-gas manufacturer: Any western Kentucky producer may ship coal of special quality for special uses to points of delivery within the prohibited territory under permit which may be obtained from the Fuel Administration on application of the consumer. 10 WATER-GAS MANUFACTURE The inspection reveals that there are still many operating prob- lems to be solved ; and that a further study of these will be of benefit to the gas industry. Consequently, this circular is only preliminary to the publication of the results of further investigations which are being undertaken by the cooperating agencies. OBJECTIONS OFFERED TO THE USE OF BITUMINOUS COAL AS GENERATOR FUEL At some plants operators have been deterred from using bitum- inous coal as generator fuel because of difficulties expected on the basis of their experience with coke fuel. It is usually anticipated that the coking or matting together of the fresh coal in the generator will obstruct the passage of blast and steam through the fire, thereby lead- ing to the formation of flues through the fuel bed with consequent decreased capacity and efficiency of the generating set. The large amount of volatile matter which is released when fresh coal is charged into the generator is another anticipated cause of difficulty. Not only is the fear of creating a smoke nuisance a deterrent with some oper- ators whose plants are located where complaints would likely arise, but the ill effect of this large amount of volatile matter upon the oper- ation of the plant is feared. It is often anticipated that if an effort is made to burn all of this volatile matter in the machine or at the stack, these parts of the apparatus will be seriously overheated, result- ing not only in upsetting the operating balance but also, perhaps, in injury to the machine itself. Some operators also anticipate that the operation of the hot valves will be impeded by the tar present in the gases given off by the generator and that the checker bricks in the car- buretor and superheater will be fouled rapidly ; also that the purifying' equipment of the plant will be overloaded by excessive sulphur in the gas. On account of the relatively low melting point of the ash from most central district coals, as shown when cokes from these coals are used as generator fuel, the formation of excessive . and troublesome clinker has also been expected from the use of these coals. In general, these difficulties have been met and overcome. It is true that the average figures at the twenty plants visited showed a decreased capacity of the set of about 25 per cent when using coal in place of coke, and an increase of about 30 per cent in the amount of fuel needed for making 1,000 cubic feet of gas. However, the cost of coal being less than coke, and the amount of oil necessary being decreased about 10 per cent, the actual cost of gas per 1,000 cubic feet decreased wdien coal was used. OBJECTIONS TO BITUMINOUS COAL 11 METHODS OF OVERCOMING OBJECTIONS When the central district coals are charged into a water-gas gen- erator in the same volume as coke would be charged, a rather dense firm mat of coke is formed on blasting. The mat arches over the top and does not drop without being poked from the charging door. This property of matting when heavy charges are used, naturally increases the tendency to form flues or chimneys in the fuel, and reduces the capacity and operating efficiency of the machine. To overcome this caking difficulty, coal must be charged into the generator in much smaller quantities by volume than coke, since coal is heavier per unit of volume. Some operators, particularly those handling the larger sets, carry a deeper fuel bed than they would otherwise consider possible, by making "split" steam runs ; that is, they reverse the direction of flow of steam through the fire while the run is in progress. At a few plants some trouble has been experienced from smoke, especially where the plant is located in a residence district. Any smoke in these districts results in immediate complaint. It is very difficult to avoid smoke or oil fumes at all times even with coke fuel. With coal the trouble is increased because it is especially difficult to com- pletely burn the hydrocarbons given off from the incomplete combus- tion of coal in the machine during the early stages of the heating-up period when the checker bricks in the carburetor are not hot enough to ignite these gases. Where a set is operated to almost its full capacity, these bricks will not usually cool off so much during lay-over periods that any great difficulty will be experienced in quickly igniting the generator gases, but in a plant operating but a few hours a day the problem is greater. One ingenious operator has hastened the ignition by means of an automobile spark plug screwed into a short length of pipe extending above the carburetor. With this device he is able to ignite the gases passing into the carburetor long before the bricks would become hot enough to ignite them. At the same time the heat- ing up of the carburetor and superheater is hastened. In order to reduce the smoke formed after coaling the machine, some operators blast before coaling and make a steam run before blasting again. The prevention of the overheating of carburetor and superheater during the blasting period lies in the proper timing of this operation. It is generally accepted that on blasting coal containing a high per- centage of volatile matter a gas will be produced containing some of the hydrocarbons of the volatile matter of the coal. Such blast gases are higher in heating value than the blast gases from coke, and when burned in the machine they produce more heat in the carburetor and 12 WATER-GAS MANUFACTURE superheater. Therefore, a long blast on such a fuel as central dis- trict bituminous coal will result in the production of more heat than is required for cracking and fixing the carburetting oil. This means that the gas in excess of the amount required for the proper heating of the checker brick has to be burned at the stack. Not only is this a wasteful process, but it so heats the stack that there is danger of melting it. Therefore prolonged blasting such as is sometimes prac- ticed with coke, is undesirable when bituminous coal is used as a gen- erator fuel. More tar is formed with coal as generator fuel than with coke, the average increase noted being 25 per cent. Under some conditions it causes the valves, and particularly the hot valve, to stick or work less freely. While this excess of tar need not cause any serious trouble, most operators take precautionary measures. Sometimes dis- tillate or paraffin oil is poured down the stem of the hot valve after completing the day's run to soften the tar. The tar trouble may also be diminished by tapping a hole in the valve bonnet and pouring a little lubricating oil into the valve through this opening once a day. Actual practice indicates that the coals from southern Illinois and from Indiana containing less than 1^ per cent of sulphur have not caused any sulphur trouble when used in the manufacture of water- gas. One gas company reports that the unpurified gas from these coals contains only 5 per cent more sulphur than the water-gas manufac- tured from coke, using the same kind of oil in both cases. Some operators state that the gas manufactured with bituminous coal purifies more easily than that produced when using coke fuel. Serious sulphur trouble has not been noticed in any of the gas plants visited. From the experience of various operators with central district coals, it seems that the fear of an excessive deposit of carbon in the checker bricks resulting from the use of coal, is largely groundless. At only one of the plants visited was any abnormal deposition of carbon reported. In this case a loose deposit of carbon in the shape of an inverted cone was said to form in the interstices of the superheater checker bricks, the apex of the cone being near the bottom of the checker work and the base of the cone near the top, where it extended to within a foot of the wall. The set was 8 feet 6 inches in diameter and was operated 24 hours a day. A sample of the carbon analyzed carried over 98 per cent combustible matter, showing that it was deposited carbon and not coal dust. In operating this machine some of the blast gas was burned outside the machine at the stack. The operating cycle consisted of a three-minute blast and a four-minute steam run; the blast pressure was 16 inches. The steam used was USE OF BITUMINOUS COAL 13 40 to 45 pounds per minute, and alternate up and down runs were made. In those Illinois gas plants where good results with coal are being obtained without the formation of carbon, the method of opera- tion is to employ a greater blast pressure, a shorter time of blast, and a greater amount of steam per minute during the runs than is used when coke is the generator fuel. By using what appears to be an excessive amount of steam, the temperatures of the carburetor and superheater are reduced to such an extent that the gas produced in the subsequent blast can be burned entirely within the machine without overheating it. With this practice no carbon troubles are experienced in the superheater. The fusing point of the ash of central-west coal is lower than that from eastern coke; therefore, to avoid clinker, which is simply ash fused or melted together, it is necessary to avoid unduly high temperatures. For this reason, if the fuel bed is not blasted too long and the air pressure is not too high, little clinker trouble need result. As will be noted in a later section of this circular, there is a tendency among operators to use relatively more steam with coal than with coke, which practice together with the blasting method employed usually results in a clinker which is more easily broken up than the clinker from coke. WATER-GAS MANUFACTURE AT PLANTS USING BITUMINOUS COAL FUEL As a result of the inspection of water-gas plants using bituminous coal, it is possible to discuss the principal points in operating practice which seem essential to success. The advantages and disadvantages of any particular method of operation or the detailed chemical reac- tions of the water-gas process will not be discussed in this circular. The following variables seem to be most important : 1. Kind and size of fuel. 2. Depth of fuel bed and its relation to blast and steam cycle. 3. Quality and quantity of oil used. 4. Distribution of oil in the carburetor. 5. Temperature maintained in the carburetor and in the super- heater. 6. Purging the machine with air. Each of these variables has so important a bearing upon the operating results, and all are so inter-related that a change in one condition almost invariably necessitates a change in others if the heat balance in the 14 WATER-GAS MANUFACTURE machine, necessary to good operation, is to be maintained. It is not possible to predict exactly what combination of conditions will be necessary in each case. In the following, the tendencies of present practice, rather than absolute results obtained when changing from coke to coal, will be discussed. Kind and Size of Fuel The coal now used is either low-sulphur coal from seam No. 6 in southern Illinois or from seam No. 4 in western Indiana. Other bituminous coals from the central ditsrict, if low in sulphur, could probably be used successfully. The smaller plants use lump coal about 5 inches in diameter. Lumps larger than these are broken up with a sledge while the charging buggy is being filled, and fine coal is removed by forking. In the larger plants it is the practice to use egg- size coal or lumps between 2 and 6 inches in diameter, which is charged into the generator without preliminary breaking. Depth of Fuel Bed and Its Relation to Blast and Steam Cycle The depth of the fuel bed maintained in the generator and the blast and steam pressure carried during operation are so closely inter- related that they may well be discussed together. The effect of a thin fuel bed in reducing the tendency of the fuel to mat together has already been discussed. Most operators find that the fuel can best be maintained at the desired depth by coaling the generator more fre- quently and with a smaller weight of charge than when using coke. Several operators state that the weight of the coal charge should be about 80 per cent of the weight of the coke charge, and that one or two fewer runs should elapse between charging times. A decreased depth of fuel bed permits the passage of more air or steam through the fire in a given time at a given pressure. Since the amount of air required to bring the fuel bed to the proper con- dition varies roughly with the amount of fuel, a shallow fire requires less blast than a deep fire. With bituminous coal most operators not only blast at about 2 to 3 inches water pressure less than when using coke, but also decrease the length of the blasting period. With a shallower bed of incandescent fuel for the steam to act upon, it might be expected that the duration of the steam run and the amount of steam used per minute should be decreased in order to maintain the heat balance in the set. However, in the majority of plants visited the steam was not decreased in the same proportion as was the air blast, and the length of run was usually the same as with USE OF BITUMINOUS COAL 15 coke. A very common cycle was a 2-minute blast followed by a 4-minute steam run. A 3-minute blast followed by a 5-minute run was also frequently observed. In the matter of proportioning the "up" and "down" runs there was a great difference of opinion. Some operators alternated the up and down runs after the set had been brought to normal running con- ditions. Others made more down runs than up runs, while still others favored more up runs. A few preferred to "split" every run as here- tofore discussed. It was quite common practice in the plants inspected to use about 10 pounds more of steam per minute on the down runs than on the up runs. The operating conditions observed suggest that much benefit can be derived from the study of the composition of the generator gases produced under various conditions of operation and the determina- tion of the amount of steam passing through the fire undecomposed. The conditions actually maintained in some plants were impos- sible to ascertain. The poor condition or lack of steam and air gauges and meters in several cases made experimental work with a view to bettering operating conditions almost impossible. In a few cases, care- lessness or ignorance of those actually handling the machine was the principal handicap to good results. Quality and Quantity of Oil Used The quality of oil used in a given plant will of course affecl the operation and have a pari in determining the proper cycle. The concensus of opinion seems to be that oils from different fields require different heat treatment, and so it is impossible to prescribe operating conditions without taking the kind of oil into account. I lowcvcr, assuming that a change is made from coke to coal fuel, there are cer- tain differences to be observed in operation. The so-called "blue gas" produced from bituminous coal fuel is higher in heating value than the "blue gas" from coke since it con- tains a considerable percentage of hydrocarbons. Consequently less oil is required per 1,000 cubic feet of gas to enrich to the required standard. The reduction in the amount of oil required may be as much as 0.5 gallon per thousand cubic feet of gas made. Since the amount of gas made per run is usually less with coal than with coke, the amount of oil required per run is of course less. To fix the oil the same temperatures are usually maintained in the carburetor and super- heater as when using coke fuel. These temperatures range from 1250° F. to 1350°F. 16 WATER-GAS MANUFACTURE Distribution of Oil in the Carburetor In changing to coal fuel, the oil spray in the carburetor is often left as it was when coke was used. The result is that with a decreas- ing oil requirement per run, it is necessary to reduce the rate of oil flow through the nozzle and frequently this reduction results in poor distribution. Instead of spraying, uniformly over the surface of the bricks in the top of the carburetor, much of the oil may pass down through the center of the carburetor, resulting in incomplete vapori- zation and low oil efficiency. As a consequence a large portion of the oil is wasted. Furthermore the concentration of oil in the center of the carburetor may cause the formation of an excessive deposit of carbon which fouls the checker bricks and soon necessitates recheckering. This matter should have the immediate attention of any operator mak- ing the change. Purging the Machine with Air In some plants it is the practice to purge the machine with air after completing the steam run and before raising the stack valve. There is evidently a gain by doing this, although oftentimes it is car- ried so far that the dilution of the gas by the lean-air gas thus manu- factured makes necessary the use of an excessive amount of oil to bring the gas to the required B. t. u. standard. By watching the quality of the gas the operator can estimate how far he can carry this purging process. One advantage in purging not usually considered is that during this purging carbon is being burned in the generator, thus caus- ing a rise of temperature in the fuel bed; and at the same time the carburetor and superheater are being heated less than during the regular blast period when blast gas is being burned in these chambers. Since the usual tendency in operation is to allow the superheater to become too hot, this process of purging may give the operator greater control over the temperature. As a precautionary measure, before opening the air blast to purge, the operator should make sure that the blower is up to speed, so that there will be sufficient pressure in the air lines to prevent back firing in the blast line. OPERATING DATA FROM TYPICAL PLANTS WHERE COAL IS USED AS GENERATOR FUEL At several plants where both water-gas and coal-gas are manu- factured they are not metered separately. In these cases it is usual to estimate the yield of coal-gas from the amount of coal carbonized OPERATING DATA 17 and to estimate the amount of water-gas as the difference between the combined yield and the estimated coal-gas yield. Operating data from these plants can not be used for accurate comparison. It was possible, however, to obtain data from several plants where water-gas only was manufactured and at others where the water-gas was metered separately. It should be remembered that results obtained at any particular plant depend not only on the operating methods, but on the quality and kind of fuel and oil and on the general equipment and its physical condition. As bituminous coals from only a few mines in the central district have been used in water-gas manufacture, no comparison of different coals is possible at this time. Also since the use of bituminous coal is new, the operating conditions have not been fully standardized, and each operator is using individual operating methods. Although the data furnished by the operators was given as average practice, yet the desire to report the best results should be taken into consideration. At some plants the facilities for weighing the fuel were poor and therefore the figures given for fuel consumption may be approximate only. The operating data selected from four typical plants are given in the table following : 18 WATER-GAS MANUFACTURE cU-S g 00 CO c *-' O 10 CM c*i ° 3 CM o 00 rt CM ' © CM c c oo a; - " CNlO rj o o vo D •S Ofi n K. * i & CC (0 • O Co a o'jS o g -m i* cj C 3l§Ec S " V "> © lo CS g"o >> o *° 3 £ CM So 2 " cm' *> ""*■ CM 00 m t-lCM ''si ti rt cO o o o . >> -r en rt VO ^_ o c P O CM t^ " 00 CM CM M h *0 i«) « .S.s . s ^ si § <+- ° 5 a. o CD CD fill g a e E - * a, bi cs ii J3 = r" JT cO cO <- O fa < in w K E £ !3 ■ J _o a; be SoQ 3 3 3 F. - SI P U cfl a o u o K H l, 5 en a n a E e, ^ rt en